Backlight systems which comprise a plurality of segments for selectively illuminating a predefined area of pixels are known per se, and are also known in the art as two-dimensional dimmable backlighting systems. They are used, inter alia, as light sources in (picture) display devices, for example, for TV sets and monitors. Such illumination systems are particularly suitable for use as backlighting systems for non-emissive display devices such as liquid crystal display devices, also denoted LCD panels, which are used in, for example, (portable) computers or, for example, (portable) telephones.
Said non-emissive display devices usually comprise a substrate provided with a regular pattern of pixels which are each controlled by at least one electrode. The display device utilizes a control circuit for achieving a picture or a data graphical display in a relevant field of a (picture) screen of the (picture) display device. The light originating from the backlighting system in an LCD device is modulated by means of a switch or modulator in which, for example, various types of liquid crystal effects may be used. In addition, the display may be based on electrophoretic or electromechanical effects.
Such a backlighting system for illuminating an image display device is known from US patent application US 2007/0024772, which discloses a matrix of liquid crystal elements and a plurality of direct backlight devices. Each direct backlight device is configured to selectively illuminate a discrete portion of the matrix of the liquid crystal elements associated with a backlighting sub-region with a temporal sequence of at least two illumination color lights during an image frame period. The known backlight device comprises sub-region barriers which separate one sub-region from another preventing light from one sub-region from leaking into an adjacent sub-region.
A drawback of this known backlighting device is that additional measures for creating overlap between segments are added, which increase the thickness of the known backlighting system.